1. Introduction

The natural range of Apis mellifera includes Africa and Eurasia. In addition, this species has been introduced by humans to all other continents except Antarctica and is used intensively in pollination and honey production all over the world.

In this chapter, we place a stronger focus on the natural diversity within Europe than elsewhere for several reasons: (i) the diversity situation and the status of subspecies and ecotypes in Europe is known best, (ii) bee diversity research and breeding efforts in many parts of Africa and Asia are still in their infancy, (iii) most subspecies utilized for breeding (including the New World) originate from Europe. However, the approach and the methods discussed are of course valid for all populations of A. mellifera from its entire range.

Honey bees show considerable geographical variation, resulting in adaptation to regionally varying factors of climate and vegetation, but also to prevailing pests and pathogens. However, this natural heritage is increasingly subject to diffusion by human beekeeping efforts at a worrisome speed. The demand for high economic performance of bee colonies, combined with desirable behavioural characteristics, has led to considerable changes caused by systematic bee breeding. Thus, the original geographic distribution pattern is being dissolved EU-wide by mass importations and an increasing practice of queen trade and colony movements. These activities endanger regional races and ecotypes by promoting hybridization (De la Rúa et al., 2009, Meixner et al., 2010), and by adding various breeder lines with distinct properties to the picture. Yet another dimension is added by the deliberate replacement of native subspecies in some regions by non-native bees with more desirable characters and greater commercial interest (for instance, the replacement of A. m. mellifera in northern and central Europe by A. m. carnica or A. m. ligustica) (Bouga et al., 2011).

The downside of these economically driven processes is an increasing trend towards uniformity of honey bee populations across Europe, leading to a loss of both genetic diversity and specific adaptations to local conditions (reviewed in De la Rua et al., 2009; Meixner et al., 2010).

Honey bees are particularly sensitive to inbreeding (Seeley and Tarpy, 2007 and references therein). Therefore, the loss of genetic diversity is of grave concern. It has been shown that colonies with reduced genetic diversity are less capable of controlling hive temperature (Jones et al., 2004) and more prone to develop diseases when challenged by parasites (e.g. Tarpy, 2003). This reduction in genetic diversity may also affect the capacity of honey bee populations to adapt to new threats, such as newly introduced parasites like varroa.

Thus, there is a widely recognized need to encourage regional breeding efforts to preserve local adaptation and, to maintain local strains in isolated conservation apiaries. To attain this goal, it is necessary to have a reference base to identify strains to be used for breeding. To provide a stable baseline, it is important that this reference reflects the natural variation of honey bees, since beekeepers and breeders are known to often work with non-native stock. However, although the rough outlines of the original patterns of honey bee diversity have more or less been clarified, many of the details are still "work in progress". Ten of the currently 27 described subspecies can be found in Europe, but considerable variation can be observed within many of them and several can be further subdivided into a diversity of "ecotypes". Several subspecies and ecotypes can be considered as endangered (De la Rúa et al., 2009). Other than subspecies which can be assigned a formal trinomen according to the ICZN, there is no formal definition for ecotypes.  However, the ecotype concept may include any regional natural bee type distinct enough to raise the need for a name. In addition to these refinements, the scientific description and recognition of honey bee diversity in Europe cannot be regarded as complete, since vast areas, predominantly in the eastern part of the continent, have not yet been studied systematically. Table 1 summarizes the current state of knowledge regarding honey bee subspecies and ecotypic variation in Europe.

Historically, the current picture of honey bee geographic variation has emerged gradually over time from the results of numerous publications. Up to now, the most comprehensive compilation is still provided by the monograph of Ruttner (1988), based on the application of numerical taxonomy using characters of "classical" morphometry. Since then, many details to the contours of this basic picture have been added by others. However, as methods differ due to the varying preferences of different researchers, and the results achieved using different techniques are oftentimes not congruent, there is now a critical need to integrate data bases, make reference data sets generally accessible, and harmonize procedures to achieve sound and generally recognized "consensus reference data sets". To date, different laboratories keep independent reference samples, and there are still considerable gaps in relating molecular results to classical morphometric group definitions. In short, there is no agreement on a common procedure yet, raising a strong need to work towards an accessible data base of European subspecies and ecotypes, integrating records obtained with different methods and serving as reference for future research projects and identification needs.

Having pointed out these shortcomings and aims for improvement, nonetheless, methods for characterization and identification of honey bees on the morphological and the molecular level have reached a fairly sophisticated stage. Our aim with this paper is to give recommendations and detailed descriptions for a variety of morphological and molecular methods in order to facilitate the acquisition of data compatible for integration towards a more coherent capture of the diversity of honey bees in Europe and the world.

Table 1. Current status of honey bee subspecies and ecotypes in Europe (the references given here are meant as examples, and not as an exhaustive list of all studies performed).

Subspecies name

Status of knowledge


Morphometric lineage

Mitochondrial lineage

Morphometric references available?

mtDNA references available?

Studies on the COI-COII intergenic region are printed in bold

Microsatellite references available?

A. m. mellifera

Despite the fact that the original description of Apis mellifera by Linnaeus was on this bee and this subspecies has the widest range of all A. mellifera subspecies, surprisingly little information is available. This race has been comparatively well studied in the western part of its range, especially in France and Britain, and also in southern Scandinavia.

Almost nothing is known about the extent of its range and its variability towards the east, beyond Poland.  Older literature from Russia often restricted to description of single characters (e.g. tongue length).

Ecotypic variation has been described and confirmed in France (Louveaux et al., 1966; Strange et al., 2007), where also several conservation areas have been established

M

M

yes
Ruttner, 1988

Meixner et al., 2007

 

yes
Smith and Brown, 1990

Franck et al., 1998

Garnery et al., 1998a

Jensen et al., 2005

Rortais et al., 2011

yes
Franck et al., 1998

Garnery et al., 1998b

Jensen et al., 2005

 

A. m. ligustica

Comparatively well studied

Ecotypic variation not known, likely to be diffused by colony movements

 

C

C(M)

yes

Ruttner, 1988

Nazzi, 1992

yes

Franck et al., 2000

yes

Franck et al., 2000

Dall’Olio et al., 2007

A. m. carnica

Well studied in Austria, Slovenia and Croatia, few studies from eastern part of range

Ecotypic variation postulated (e.g. Alpine and Pannonian ecotypes, Ruttner 1988) but few data

C

C

yes

Ruttner, 1988

Meixner et al., 1993

Dedej et al., 1996

Mladenovic et al., 2011

Marghitas et al., 2008

 

Reka et al., 2007

 

yes

Smith and Brown, 1990

Meixner et al., 1993

Sušnik et al., 2004

Muňoz et al., 2008

Nedić et al., 2009

yes

Muňoz et al., 2008

A. m. macedonica

 

Few publications

The subspecies extends from the southern Balkan to Ukraine, but the true range is not yet known

Ecotypic variation hypothesized, but no internationally available description

C

C

yes

Ruttner, 1988

Uzunov et al., 2009

yes

Bouga et al., 2005

Ivanova et al., 2010

Stevanovic et al., 2010

yes

Uzunov et al., 2013

A. m. iberiensis

 

Well studied in most of Iberian Peninsula

No distinct ecotypic variants found for the mainland, but ecotypes described for island populations

M

M/A

yes

Ruttner, 1988

Arias et al., 2006

Cornuet and Fresnaye, 1989

Padilla Alvarez et al., 1998, 2001

Radloff et al., 2001

yes

Smith et al., 1991

De la Rúa et al., 1998

De la Rúa et al., 2001a

De la Rúa et al., 2001b

De la Rúa et al., 2002

Arias et al., 2006

Canovas et al., 2008

 

yes

De la Rúa et al., 2003

De la Rúa et al., 2006

Miguel et al., 2007

Miguel et al., 2010

Canovas et al., 2011

A. m. cecropia

Very few studies, current status questionable

C

C

yes

Ruttner, 1988

yes

Bouga et al., 2005

no

A. m. siciliana

Little studied, near extinct

C/A

A

yes

Ruttner, 1988

yes

Sinacori et al., 1998

Franck et al., 2000

no

A. m. cypria

Few studies

C

C/Z

yes

Ruttner, 1988

Kandemir et al., 2000

yes

Kandemir et al., 2006

yes

Kandemir et al., 2006

A. m. anatoliaca

 

Some studies

Possible ecotypic variation in western Anatolia (Aegean region), but few data available; more variation may be possible

O

 

C/Z

yes

Ruttner, 1988

Kandemir et al., 2000

yes

Palmer et al., 2000

Kandemir et al., 2006

 

yes

Bodur et al., 2007

A. m. caucasica

 

Despite its economic importance there are substantial gaps in our knowledge about this subspecies. Some data are available from the northern part (Ukraine, Russia), and very few from the southern Caucasus (Turkey).

Ecotypic variation seems possible but not studied.

O

C

yes

Ruttner, 1988

yes

Kandemir et al., 2006

yes

Bodur et al., 2007

A. m. adami

 

Sparse information

C

C

yes

Ruttner, 1980, 1988

yes

Bouga et al., 2005

no

A. m. ruttneri

 

Only one study. Current fate of population unknown

M/A

A

yes

Sheppard et al., 1997

yes

Sheppard et al., 1997

no